This invention relates to medical devices, in particular a delivery system for implantation of powders or fine particles in surgical procedures and, more particularly, this invention relates to an absorbable collagen tube or pouch for the containment of fine particles for surgical implantation. In a preferred embodiment, this invention relates to the aforementioned delivery system as used in dental surgery, that is, in alveolar ridge augmentation.
It is quite common for the bone of the mandible and the maxilla of older individuals to have resorbed during their lifetime to the extent that in the case of the mandible it is too thin and weak to support dentures and presents a high risk of fracture. In such instances of severely atrophic mandible or maxilla, procedures have been developed wherein the oral surgeon builds up the height and width of the alveolar ridge with autogenous cancellous bone or in more recent years by introducing non-resorbable hydroxylapatite or related resorbable tricalcium phosphate into a tunnel made in the periosteum covering the mandible or maxilla. It has been found that hydroxylapatite which makes up the bulk of the human skeletal system, ranging from approximately 65% of bone to 98% of dental enamel is biocompatible and well tolerated and in time becomes well bonded to the natural bone. New bone grows around and incorporates the particles of hydroxylapatite.
The usual procedure employed by the oral surgeon in placing the hydroxylapatite particles in close proximity to the mandibular or maxillary bone is to make a subperiosteal tunnel or pocket and with a delivery syringe introduce the fine particles of sterile hydroxylapatite or tricalcium phosphate alone or in combination with autogenous bone chips admixed with sterile saline. Although this procedure has been successful in augmentation of the alveolar ridge, it has certain limitations. The particles of hydroxylapatite or tricalcium phosphate lack form and cohesive strength and tend to migrate into the neighboring tissue and also are dislodged under externally applied forces. The syringe delivery system offers further limitations in particle placement. These prior art procedures are well-documented in the literature as, for instance, in Frame et al., "hydroxyapatite as a Bone Substitute in the Jaws," Biomaterials, 2, January 1981, pp. 19-22; The Compendium of Continuing Education in Dentistry, Supplement No. 2, 1982, pp. S45-S85; Cranin et al., "Human Mandibular Alviolar Ridge Augmentation with Hydroxylapatite a Four Year Analysis," 9th Annual Meeting of the Society for Biomaterials, Apr. 27-May 1, 1983, p. 25; dePutter et al., "In Vivo Fatigue Behaviour of Permucosal Dental Implants of Calciumhydroxylapatite, Comparing Non-Prestressed with Prestressed Implants," 9th Annual Meeting of the Society for Biomaterials, Apr. 27-May 1, 1983, p. 27; Niwa et al., "Preparation of Porous and Granule Hydroxyapatite and Possibility of Application as a Bone Graft," 9th Annual Meeting of the Society for Biomaterials, Apr. 27-May 1, 1983, p. 24; Calcitek, Inc., "Calcitite Brand of Hydroxylapatite (Dense, Nonresorbable) a New Solution for Alveolar Bone Restoration;" Calcitek, Inc., "Calcitite 2040 Nonresorbable Hydroxylapatite Bone Grafting Material for Alveolar Ridge Augmentation," June 18, 1982; Cook-Waite Laboratories, Inc., "Alveograf Brand of Durapatite (18-40 Mesh) Alveolar Ridge Bone-Grafting Implant Material," June 1982; Cook-Waite Laboratories, Inc., "A New, Nonresorbable Bone-Grafting Implant that Restores Alveolar Ridge Height and Width Permitting Denture Construction in a Matter of Weeks;" and Miter, Inc., "Augmen a Synthetic Bone Grafting Material Which is Replaced by New Bone as it Resorbs-For Physiological Augmentation of Alveolar Ridges." See also Misiek et al., "The Inflamatory Response to Different Shaped Hydroxylapatite Particles Implanted in Soft Tissue," 9th Annual Meeting of the Society for Biomaterials, Apr. 27-May 1, 1983, p. 23.
In addition to the forms of hydroxylapatite discussed above which are used for alveolar ridge augmentation, other form of hydroxylapatite, demineralized bone, and other similar materials have been used as prosthetic materials. U.S. Pat. No. 4,097,935 discloses a hydroxylapatite ceramic for use as a dental restorative composition and a prosthetic material. Calcium phosphate ceramics are also discussed as prosthetics by Jarcho, in "Calcium Phosphate Ceramics as Hard Tissue Prosthetics," Clinical Orthopaedics, 157, June 1981, pp. 259-278. See also Kranen et al., "The Use of Durapatite in Maxillofacial Reconstruction," 9th Annual Meeting of the Society for Biomaterials, Apr. 27-May 1, 1983, p. 26; and Mulliken et al., "Use of Demineralized Allogeneic Bone Implants for the Correction of Maxillocraniofacial Deformities," Annals of Surgery, 194, No. 3, September 1981, pp. 366-372.
The main problems associated with the use of powdered hydroxylapatite, tricalcium phosphate, autogenous cancellous bone, or demineralized bone for alveolar ridge augmentation are the migration of the mineral powder and the resorption of the powder. There is also the possibility of an inflamatory response based on the shape of the particles. There has been an attempt at solving some of these problems by encapsulating the particles in a casing made of a woven or non-woven fabric. This is disclosed in U.S. Pat. No. 4,430,760 which issued to Thomas L. Smestad on Feb. 14, 1984. The Smestad patent, teaches the use of cancellous or compact bone, or dentin, which has been comminuted to a particle size in the range of about 40 to 500 microns and contained within a "porous" casing which is a woven or non-woven fabric. Typical woven fabrics are Dacron, Nylon, and Carbon fabrics. Typical non-woven fabrics are disclosed as being made of collagen, polyesters, polyamides, and polyolefins. It is a requirement of the Smestad invention that the maximum pore size of the fabric is less than the smallest particles size of the bone or dentine powder. There is a disadvantage associated with the use of the woven and non-woven fabrics, namely, the synthetic polymers used are not bioerodible. In addition, it is clear from the disclosure of the Smestad Patent that all the fabrics used are microporous. The pore size is too small to allow migration of cells into the package. Thus, the Smestad prosthesis suffers from the same disadvantages as the other prior art techniques.